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Up until now, freeing payloads on remote MST hubs that just had ports
removed has almost never worked because we've been relying on port
validation in order to stop us from accessing ports that have already
been freed from memory, but ports which need their payloads released due
to being removed will never be a valid part of the topology after
they've been removed.
Since we've introduced malloc refs, we can replace all of the validation
logic in payload helpers which are used for deallocation with some
well-placed malloc krefs. This ensures that regardless of whether or not
the ports are still valid and in the topology, any port which has an
allocated payload will remain allocated in memory until it's payloads
have been removed - finally allowing us to actually release said
payloads correctly.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Cc: David Airlie <airlied@redhat.com>
Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Juston Li <juston.li@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-10-lyude@redhat.com
While this isn't a complete fix, this will improve the reliability of
drm_dp_get_last_connected_port_and_mstb() pretty significantly during
hotplug events, since there's a chance that the in-memory topology tree
may not be fully updated when drm_dp_get_last_connected_port_and_mstb()
is called and thus might end up causing our search to fail on an mstb
whose topology refcount has reached 0, but has not yet been removed from
it's parent.
Ideally, we should further fix this problem by ensuring that we deal
with the potential for racing with a hotplug event, which would look
like this:
* drm_dp_payload_send_msg() retrieves the last living relative of mstb
with drm_dp_get_last_connected_port_and_mstb()
* drm_dp_payload_send_msg() starts building payload message
At the same time, mstb gets unplugged from the topology and is no
longer the actual last living relative of the original mstb
* drm_dp_payload_send_msg() tries sending the payload message, hub times
out
* Hub timed out, we give up and run away-resulting in the payload being
leaked
This could be fixed by restarting the
drm_dp_get_last_connected_port_and_mstb() search whenever we get a
timeout, sending the payload to the new mstb, then repeating until
either the entire topology is removed from the system or
drm_dp_get_last_connected_port_and_mstb() fails. But since the above
race condition is not terribly likely, we'll address that in a later
patch series once we've improved the recovery handling for VCPI
allocations in the rest of the DP MST helpers.
Changes since v1:
* Convert kerneldoc for drm_dp_get_last_connected_port_and_mstb to
normal comment - danvet
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@redhat.com>
Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Juston Li <juston.li@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-8-lyude@redhat.com
The current way of handling refcounting in the DP MST helpers is really
confusing and probably just plain wrong because it's been hacked up many
times over the years without anyone actually going over the code and
seeing if things could be simplified.
To the best of my understanding, the current scheme works like this:
drm_dp_mst_port and drm_dp_mst_branch both have a single refcount. When
this refcount hits 0 for either of the two, they're removed from the
topology state, but not immediately freed. Both ports and branch devices
will reinitialize their kref once it's hit 0 before actually destroying
themselves. The intended purpose behind this is so that we can avoid
problems like not being able to free a remote payload that might still
be active, due to us having removed all of the port/branch device
structures in memory, as per:
commit 91a25e4631 ("drm/dp/mst: deallocate payload on port destruction")
Which may have worked, but then it caused use-after-free errors. Being
new to MST at the time, I tried fixing it;
commit 263efde31f ("drm/dp/mst: Get validated port ref in drm_dp_update_payload_part1()")
But, that was broken: both drm_dp_mst_port and drm_dp_mst_branch structs
are validated in almost every DP MST helper function. Simply put, this
means we go through the topology and try to see if the given
drm_dp_mst_branch or drm_dp_mst_port is still attached to something
before trying to use it in order to avoid dereferencing freed memory
(something that has happened a LOT in the past with this library).
Because of this it doesn't actually matter whether or not we keep keep
the ports and branches around in memory as that's not enough, because
any function that validates the branches and ports passed to it will
still reject them anyway since they're no longer in the topology
structure. So, use-after-free errors were fixed but payload deallocation
was completely broken.
Two years later, AMD informed me about this issue and I attempted to
come up with a temporary fix, pending a long-overdue cleanup of this
library:
commit c54c7374ff ("drm/dp_mst: Skip validating ports during destruction, just ref")
But then that introduced use-after-free errors, so I quickly reverted
it:
commit 9765635b30 ("Revert "drm/dp_mst: Skip validating ports during destruction, just ref"")
And in the process, learned that there is just no simple fix for this:
the design is just broken. Unfortunately, the usage of these helpers are
quite broken as well. Some drivers like i915 have been smart enough to
avoid accessing any kind of information from MST port structures, but
others like nouveau have assumed, understandably so, that
drm_dp_mst_port structures are normal and can just be accessed at any
time without worrying about use-after-free errors.
After a lot of discussion, me and Daniel Vetter came up with a better
idea to replace all of this.
To summarize, since this is documented far more indepth in the
documentation this patch introduces, we make it so that drm_dp_mst_port
and drm_dp_mst_branch structures have two different classes of
refcounts: topology_kref, and malloc_kref. topology_kref corresponds to
the lifetime of the given drm_dp_mst_port or drm_dp_mst_branch in it's
given topology. Once it hits zero, any associated connectors are removed
and the branch or port can no longer be validated. malloc_kref
corresponds to the lifetime of the memory allocation for the actual
structure, and will always be non-zero so long as the topology_kref is
non-zero. This gives us a way to allow callers to hold onto port and
branch device structures past their topology lifetime, and dramatically
simplifies the lifetimes of both structures. This also finally fixes the
port deallocation problem, properly.
Additionally: since this now means that we can keep ports and branch
devices allocated in memory for however long we need, we no longer need
a significant amount of the port validation that we currently do.
Additionally, there is one last scenario that this fixes, which couldn't
have been fixed properly beforehand:
- CPU1 unrefs port from topology (refcount 1->0)
- CPU2 refs port in topology(refcount 0->1)
Since we now can guarantee memory safety for ports and branches
as-needed, we also can make our main reference counting functions fix
this problem by using kref_get_unless_zero() internally so that topology
refcounts can only ever reach 0 once.
Changes since v4:
* Change the kernel-figure summary for dp-mst/topology-figure-1.dot a
bit - danvet
* Remove figure numbers - danvet
Changes since v3:
* Remove rebase detritus - danvet
* Split out purely style changes into separate patches - hwentlan
Changes since v2:
* Fix commit message - checkpatch
* s/)-1/) - 1/g - checkpatch
Changes since v1:
* Remove forward declarations - danvet
* Move "Branch device and port refcounting" section from documentation
into kernel-doc comments - danvet
* Export internal topology lifetime functions into their own section in
the kernel-docs - danvet
* s/@/&/g for struct references in kernel-docs - danvet
* Drop the "when they are no longer being used" bits from the kernel
docs - danvet
* Modify diagrams to show how the DRM driver interacts with the topology
and payloads - danvet
* Make suggested documentation changes for
drm_dp_mst_topology_get_mstb() and drm_dp_mst_topology_get_port() -
danvet
* Better explain the relationship between malloc refs and topology krefs
in the documentation for drm_dp_mst_topology_get_port() and
drm_dp_mst_topology_get_mstb() - danvet
* Fix "See also" in drm_dp_mst_topology_get_mstb() - danvet
* Rename drm_dp_mst_topology_get_(port|mstb)() ->
drm_dp_mst_topology_try_get_(port|mstb)() and
drm_dp_mst_topology_ref_(port|mstb)() ->
drm_dp_mst_topology_get_(port|mstb)() - danvet
* s/should/must in docs - danvet
* WARN_ON(refcount == 0) in topology_get_(mstb|port) - danvet
* Move kdocs for mstb/port structs inline - danvet
* Split drm_dp_get_last_connected_port_and_mstb() changes into their own
commit - danvet
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@redhat.com>
Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Juston Li <juston.li@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-7-lyude@redhat.com
drm-misc-next for v4.21, part 1:
UAPI Changes:
- Add syncobj timeline support to drm.
Cross-subsystem Changes:
- Remove shared fence staging in dma-buf's fence object, and allow
reserving more than 1 fence and add more paranoia when debugging.
- Constify infoframe functions in video/hdmi.
Core Changes:
- Add vkms todo, and a lot of assorted doc fixes.
- Drop transitional helpers and convert drivers to use drm_atomic_helper_shutdown().
- Move atomic state helper functions to drm_atomic_state_helper.[ch]
- Refactor drm selftests, and add new tests.
- DP MST atomic state cleanups.
- Drop EXPORT_SYMBOL from drm leases.
- Lease cleanups and fixes.
- Create render node for vgem.
Driver Changes:
- Fix build failure in imx without fbdev emulation.
- Add rotation quirk for GPD win2 panel.
- Add support for various CDTech panels, Banana Pi Panel, DLC1010GIG,
Olimex LCD-O-LinuXino, Samsung S6D16D0, Truly NT35597 WQXGA,
Himax HX8357D, simulated RTSM AEMv8.
- Add dw_hdmi support to rockchip driver.
- Fix YUV support in vc4.
- Fix resource id handling in virtio.
- Make rockchip use dw-mipi-dsi bridge driver, and add dual dsi support.
- Advertise that tinydrm only supports DRM_FORMAT_MOD_LINEAR.
- Convert many drivers to use atomic helpers, and drm_fbdev_generic_setup().
- Add Mali linear tiled formats, and enable them in the Mali-DP driver.
- Add support for H6 DE3 mixer 0, DW HDMI, HDMI PHY and TCON TOP.
- Assorted driver cleanups and fixes.
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/be7ebd91-edd9-8fa4-4286-1c57e3165113@linux.intel.com
Currently we may process up/down message transactions containing
uninitialized data. This can happen if there was an error during the
reception of any message in the transaction, but we happened to receive
the last message correctly with the end-of-message flag set.
To avoid this abort the reception of the transaction when the first
error is detected, rejecting any messages until a message with the
start-of-message flag is received (which will start a new transaction).
This is also what the DP 1.4 spec 2.11.8.2 calls for in this case.
In addtion this also prevents receiving bogus transactions without the
first message with the the start-of-message flag set.
v2:
- unchanged
v3:
- git add the part that actually skips messages after an error in
drm_dp_sideband_msg_build()
Cc: Dave Airlie <airlied@redhat.com>
Cc: Lyude <lyude@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Lyude <lyude@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20170719134632.13366-1-imre.deak@intel.com
Using the extension saves a bit of code.
Miscellanea:
o Neaten and simplify dump_dp_payload_table
o Removed trailing blank space from output
$ size drivers/gpu/drm/drm_dp_mst_topology.o.* drivers/gpu/drm/tinydrm/*.o*
text data bss dec hex filename
25848 0 16 25864 6508 drivers/gpu/drm/drm_dp_mst_topology.o.new
26091 0 16 26107 65fb drivers/gpu/drm/drm_dp_mst_topology.o.old
3362 2 0 3364 d24 drivers/gpu/drm/tinydrm/mipi-dbi.o.new
3376 2 0 3378 d32 drivers/gpu/drm/tinydrm/mipi-dbi.o.old
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/a78a21b5f34947da65473a0b7326922cda51a3be.1496187315.git.joe@perches.com
drm_dp_atomic_find_vcpi_slots() should be called from ->atomic_check() to
check there are sufficient vcpi slots for a mode and to add that to the
state. This should be followed by a call to drm_dp_mst_allocate_vcpi()
in ->atomic_commit() to initialize a struct vcpi for the port.
drm_dp_atomic_release_vcpi_slots() should be called from
->atomic_check() to release a port's vcpi slot allocation from the
state.
Drivers that do not make use of this atomic helper are expected to call
drm_dp_find_vcpi_slots() instead before calling
drm_dp_mst_allocate_vcpi().
v3: drm_dp_atomic_release_vcpi_slots() now needs to know how many slots
to release as we may not have a valid reference to port.
v2:
Added checks for verifying the port reference is valid
Moved get_mst_topology_state() into the helpers (Daniel)
Changed find_vcpi_slots() to not depend on current allocation
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Harry Wentland <Harry.wentland@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1492753893-3748-4-git-send-email-dhinakaran.pandiyan@intel.com
drm_dp_mst_allocate_vcpi() apart from setting up the vcpi structure,
also finds if there are enough slots available. This check is a duplicate
of that implemented in drm_dp_mst_find_vcpi_slots(). Let's move this check
out and reuse the existing drm_dp_mst_find_vcpi_slots() function to check
if there are enough vcpi slots before allocating them.
This brings the check to one place. Additionally drivers that will use MST
state tracking for atomic modesets can use the atomic version of
find_vcpi_slots() and reuse drm_dp_mst_allocate_vcpi()
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1489648231-30700-4-git-send-email-dhinakaran.pandiyan@intel.com
Pull drm updates from Dave Airlie:
"This is the main drm pull request for v4.11.
Nothing too major, the tinydrm and mmu-less support should make
writing smaller drivers easier for some of the simpler platforms, and
there are a bunch of documentation updates.
Intel grew displayport MST audio support which is hopefully useful to
people, and FBC is on by default for GEN9+ (so people know where to
look for regressions). AMDGPU has a lot of fixes that would like new
firmware files installed for some GPUs.
Other than that it's pretty scattered all over.
I may have a follow up pull request as I know BenH has a bunch of AST
rework and fixes and I'd like to get those in once they've been tested
by AST, and I've got at least one pull request I'm just trying to get
the author to fix up.
Core:
- drm_mm reworked
- Connector list locking and iterators
- Documentation updates
- Format handling rework
- MMU-less support for fbdev helpers
- drm_crtc_from_index helper
- Core CRC API
- Remove drm_framebuffer_unregister_private
- Debugfs cleanup
- EDID/Infoframe fixes
- Release callback
- Tinydrm support (smaller drivers for simple hw)
panel:
- Add support for some new simple panels
i915:
- FBC by default for gen9+
- Shared dpll cleanups and docs
- GEN8 powerdomain cleanup
- DMC support on GLK
- DP MST audio support
- HuC loading support
- GVT init ordering fixes
- GVT IOMMU workaround fix
amdgpu/radeon:
- Power/clockgating improvements
- Preliminary SR-IOV support
- TTM buffer priority and eviction fixes
- SI DPM quirks removed due to firmware fixes
- Powerplay improvements
- VCE/UVD powergating fixes
- Cleanup SI GFX code to match CI/VI
- Support for > 2 displays on 3/5 crtc asics
- SI headless fixes
nouveau:
- Rework securre boot code in prep for GP10x secure boot
- Channel recovery improvements
- Initial power budget code
- MMU rework preperation
vmwgfx:
- Bunch of fixes and cleanups
exynos:
- Runtime PM support for MIC driver
- Cleanups to use atomic helpers
- UHD Support for TM2/TM2E boards
- Trigger mode fix for Rinato board
etnaviv:
- Shader performance fix
- Command stream validator fixes
- Command buffer suballocator
rockchip:
- CDN DisplayPort support
- IOMMU support for arm64 platform
imx-drm:
- Fix i.MX5 TV encoder probing
- Remove lower fb size limits
msm:
- Support for HW cursor on MDP5 devices
- DSI encoder cleanup
- GPU DT bindings cleanup
sti:
- stih410 cleanups
- Create fbdev at binding
- HQVDP fixes
- Remove stih416 chip functionality
- DVI/HDMI mode selection fixes
- FPS statistic reporting
omapdrm:
- IRQ code cleanup
dwi-hdmi bridge:
- Cleanups and fixes
adv-bridge:
- Updates for nexus
sii8520 bridge:
- Add interlace mode support
- Rework HDMI and lots of fixes
qxl:
- probing/teardown cleanups
ZTE drm:
- HDMI audio via SPDIF interface
- Video Layer overlay plane support
- Add TV encoder output device
atmel-hlcdc:
- Rework fbdev creation logic
tegra:
- OF node fix
fsl-dcu:
- Minor fixes
mali-dp:
- Assorted fixes
sunxi:
- Minor fix"
[ This was the "fixed" pull, that still had build warnings due to people
not even having build tested the result. I'm not a happy camper
I've fixed the things I noticed up in this merge. - Linus ]
* tag 'drm-for-v4.11-less-shouty' of git://people.freedesktop.org/~airlied/linux: (1177 commits)
lib/Kconfig: make PRIME_NUMBERS not user selectable
drm/tinydrm: helpers: Properly fix backlight dependency
drm/tinydrm: mipi-dbi: Fix field width specifier warning
drm/tinydrm: mipi-dbi: Silence: ‘cmd’ may be used uninitialized
drm/sti: fix build warnings in sti_drv.c and sti_vtg.c files
drm/amd/powerplay: fix PSI feature on Polars12
drm/amdgpu: refuse to reserve io mem for split VRAM buffers
drm/ttm: fix use-after-free races in vm fault handling
drm/tinydrm: Add support for Multi-Inno MI0283QT display
dt-bindings: Add Multi-Inno MI0283QT binding
dt-bindings: display/panel: Add common rotation property
of: Add vendor prefix for Multi-Inno
drm/tinydrm: Add MIPI DBI support
drm/tinydrm: Add helper functions
drm: Add DRM support for tiny LCD displays
drm/amd/amdgpu: post card if there is real hw resetting performed
drm/nouveau/tmr: provide backtrace when a timeout is hit
drm/nouveau/pci/g92: Fix rearm
drm/nouveau/drm/therm/fan: add a fallback if no fan control is specified in the vbios
drm/nouveau/hwmon: expose power_max and power_crit
..
The i2c adapter is only relevant for some peer device types, so
let's clear the pdt if it's still the same as the old_pdt when we
tear down the i2c adapter.
I don't really like this design pattern of updating port->whatever
before doing the accompanying changes and passing around old_whatever
to figure stuff out. Would make much more sense to me to the pass the
new value around and only update the port->whatever when things are
consistent. But let's try to work with what we have right now.
Quoting a follow-up from Ville:
"And naturally I forgot to amend the commit message w.r.t. this guy
[the change in drm_dp_destroy_port]. We don't really need to do this
here, but I figured I'd try to be a bit more consistent by having it,
just to avoid accidental mistakes if/when someone changes this stuff
again later."
v2: Clear port->pdt in the caller, if needed (Daniel)
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: stable@vger.kernel.org
Cc: Carlos Santa <carlos.santa@intel.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Tested-by: Carlos Santa <carlos.santa@intel.com> (v1)
Tested-by: Kirill A. Shutemov <kirill@shutemov.name> (v1)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97666
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1477488633-16544-1-git-send-email-ville.syrjala@linux.intel.com
Not clearing mst manager's proposed vcpis table for destroyed connectors when the manager is stopped leaves it pointing to unrefernced memory, this causes pagefault when the manager is restarted when plugging back a branch.
Fixes: 91a25e4631 ("drm/dp/mst: deallocate payload on port destruction")
Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Lyude <cpaul@redhat.com>
Cc: stable@vger.kernel.org
Cc: Mykola Lysenko <Mykola.Lysenko@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
